As a public facility, the Lijiang 2.4-m telescope of Yunnan Observatories, is required to change one auxiliary instrument with another in as short a time as possible at night, in order to quickly respond to scientific programs (e.g. transient observation, time domain studies) and changes of observation conditions (e.g. seeing and weather condition). In this paper, we describe the design, construction and test of a rapid instrument exchanging system (RIES), both the hardware and software, for the Cassegrain focal station of this telescope, which enables the telescope to quickly change instruments at night without much loss of observing time. The tests in the laboratory and at the telescope show that the image quality and pointing accuracy of the RIES are satisfied. With the RIES, we observed the same Landolt standard stars almost at the same time with the Princeton Instrument VersArray 1300B Camera and the Yunnan Faint Object Spectrograph and Camera (YFOSC), both mounted at Cassegrain focus. The Quasi-simultaneous comparison shows that the image quality of the optical system inside the YFOSC is comparable with PICCD.

Recently, 1H 0323+342 has attracted a lot of attention as one of several narrow-line Seyfert 1 galaxies detected in the γ-ray band. To understand their central energy engines and jet phenomena, the black hole mass is important. We made use of the Lijiang 2.4 m Telescope to monitor 1H 0323+342 for more than two months. This galaxy is one of the candidates for a monitoring project of super-Eddington accreting massive black holes. The reverberation mapping shows that Hβ emission has a delayed response of -+ 14.8 2.7 3.9 days with respect to the SDSS g′ light curve in the rest frame. The optical Fe II variations were detected after subtracting host contaminations, and a reverberation with a delay of -+ 15.2 4.1 7.4 days was found in the rest frame. By assuming the viral factor f BLR = 6.17 for the broadline region (BLR) velocity characterized by FWHM because of the face-on orientation, we find that the black hole mass derived from Hβ is =-, and the accretion rate is M = -+ 1.11 0.47• is the mass accretion rate, L Edd is the Eddington luminosity, and c is the speed of light. This black hole is one order less massive than that given by the Magorrian relation from the bulge mass. We test the relation between accretion rates and radio-loudnesses in all mapped radio-loud active galactic nuclei, and find that 1H 0323+342 falls within this group.